Overview of cell signaling

Summary

This video provides an overview of the different ways cells communicate with each other. It starts with direct contact, where neighboring cells exchange molecules through structures like gap junctions in animal cells or plasmodesmata in plants. Cells can also communicate through complementary surface proteins or by releasing molecules into the bloodstream for long-distance signaling. These processes are classified as paracrine for short distances and endocrine for long distances. The video introduces key terms like receptors, ligands, and signal transduction, and teases future discussions on the endocrine system and hormones.

Takeaways

• 🔗 Cells can communicate directly through physical contact, like gap junctions in animal cells or plasmodesmata in plant cells.
• 🌱 Gap junctions allow small molecules to pass between neighboring cells, which can trigger responses in the receiving cell.
• 🧬 Cells can also communicate through complementary surface proteins that bind together, triggering reactions in both cells.
• 📤 Cells release signaling molecules into the extracellular space, which can bind to receptors on other cells to elicit a response.
• 🧪 Only cells with the right receptor for a particular signaling molecule will respond, while others remain unaffected.
• 📏 Short-distance signaling between nearby cells is called paracrine signaling, where paracrine factors mediate communication.
• 📡 Long-distance signaling, where molecules travel through the bloodstream, is called endocrine signaling, with hormones acting as messengers.
• 🔄 Cells can respond to their own signaling molecules in a process known as autocrine signaling.
• 🔍 Proteins that bind to signaling molecules are called receptors, and the signaling molecules themselves are called ligands.
• 🔄 Signal perception and signal transduction are key steps in cellular communication, where the binding of a ligand to a receptor triggers internal responses within the cell.

Q & A

What is the basic form of cell communication discussed in the video?

The most basic form of cell communication is through direct contact, where neighboring cells communicate by transferring molecules through gap junctions or other structures like plasmodesmata in plants.

What are gap junctions, and how do they function in animal cells?

Gap junctions are gaps in the membranes of neighboring cells that allow small molecules to pass directly from one cell to another. These molecules can trigger a response by binding to proteins in the second cell.

What is the equivalent of gap junctions in plant cells?

In plant cells, the equivalent structure to gap junctions is called plasmodesmata. These are channels that pass through both the cell walls and membranes, allowing communication between plant cells.

How can cells communicate via surface proteins?

Cells can communicate via surface proteins that bind to complementary proteins on neighboring cells. When these proteins bind, they trigger a reaction inside each cell, such as activating or releasing molecules.

What is paracrine communication?

Paracrine communication is a form of cell signaling where molecules are released by one cell and affect nearby cells over a short distance. These signaling molecules are known as paracrine factors.

What distinguishes paracrine from endocrine signaling?

Paracrine signaling affects nearby cells over short distances, while endocrine signaling occurs over long distances, where signaling molecules, like hormones, travel through the bloodstream to reach target cells.

What are the molecules called that bind to receptors on cells?

The molecules that bind to receptors on cells are called ligands. Ligands can trigger changes in the receptor protein, leading to a cellular response.

What is autocrine signaling?

Autocrine signaling occurs when a cell releases signaling molecules that bind to receptors on its own surface, leading to a response within the same cell.

What is meant by signal perception in cell signaling?

Signal perception refers to the process where a ligand binds to a receptor on the cell’s surface, triggering the beginning of the signaling process.

What happens during signal transduction in a cell?

During signal transduction, the receptor, after binding to the ligand, changes its shape or activity, leading to the transmission of the signal inside the cell, which then triggers a specific cellular response.

Outlines

00:00

🔗 Direct Cell Communication through Contact

This paragraph introduces the concept of cell communication via direct contact. It explains how neighboring cells can communicate through gap junctions (in animal cells) or plasmodesmata (in plant cells). Molecules produced by one cell can travel through these junctions to trigger reactions in the neighboring cell, thus facilitating cell signaling.

05:03

🤝 Communication via Surface Proteins

Here, the focus is on communication through surface proteins. Cells, such as those in the bloodstream, have complementary surface proteins that bind together. This binding can cause changes in the protein structure, activating reactions or signaling pathways in both cells, allowing them to communicate effectively.

📢 Signaling over Short and Long Distances

The paragraph explores cell signaling over short and long distances. It describes how cells release molecules into the extracellular space, which can bind to receptors on other cells. If the signaling occurs over a short distance, it's part of the paracrine system. If the molecules travel through the bloodstream to reach distant cells, the process is classified as endocrine signaling, and the molecules involved are referred to as hormones.

🔄 Autocrine and Endocrine Communication

This section introduces autocrine signaling, where cells can respond to the very molecules they release. It also reiterates the role of endocrine signaling over long distances and the importance of hormones in this process. Additionally, it highlights the interaction between receptors and ligands during signal perception and transduction, leading to cellular responses.

Keywords

💡Gap Junctions

Gap junctions are small channels that connect neighboring animal cells, allowing for direct communication between them by letting small molecules or ions pass through. In the video, gap junctions are described as one way that cells can communicate with each other through direct contact. This form of cell signaling is essential for coordinating activities like heart contractions.

💡Plasmodesmata

Plasmodesmata are channels between plant cells that allow communication and transport of substances across their cell walls. These are similar to gap junctions in animal cells. The video explains that when plant cells communicate directly through these channels, they are known as plasmodesmata rather than gap junctions.

💡Surface Proteins

Surface proteins are proteins located on the outside of cells that can bind with proteins from other cells, initiating various reactions or communications between them. In the video, cells with complementary surface proteins lock together to trigger a response, representing another method of direct cell-cell communication.

💡Paracrine Signaling

Paracrine signaling is a form of cell communication where cells release signaling molecules to nearby cells over a short distance. In the video, this type of communication is explained as occurring when molecules are released into the extracellular space to communicate with adjacent cells. The key example provided is the paracrine factors that affect neighboring cells.

💡Endocrine Signaling

Endocrine signaling involves communication between cells over long distances, often through hormones traveling via the bloodstream. The video describes how molecules produced by a cell can enter the bloodstream and reach distant cells with the appropriate receptors, forming part of the endocrine system.

💡Autocrine Signaling

Autocrine signaling occurs when a cell produces signaling molecules that bind to receptors on the same cell, leading to a response within itself. The video highlights this as another form of cell communication, where the cell essentially signals itself.

💡Ligand

A ligand is a molecule that binds to a receptor on a cell to trigger a response. The video explains that ligands are essential for signal transduction, where the ligand attaches to a receptor and initiates cellular communication, playing a key role in both paracrine and endocrine signaling.

💡Receptor

Receptors are proteins located on the surface or inside cells that bind to signaling molecules (ligands) to trigger a response inside the cell. In the video, receptors are discussed as crucial components in cell signaling, recognizing and binding ligands, thereby initiating processes like signal transduction.

💡Signal Transduction

Signal transduction refers to the process by which a cell converts an external signal, such as a ligand binding to a receptor, into a functional response. The video describes this as the phase where the signal is taken inside the cell, leading to various biochemical changes or cellular actions.

💡Hormones

Hormones are signaling molecules used in endocrine signaling, traveling through the bloodstream to reach distant target cells with the correct receptors. The video mentions hormones as part of the endocrine system, highlighting how they are involved in long-distance cell communication.

Highlights

- [Voiceover] What I wanna do in this video, is give ourselves a quick overview of the different ways, that cells can communicate with each other

One way could be, you just have neighboring cells, so this is one cell right over here, and this is the neighboring cell right over here

If these are plant cells, we would call these gaps, gap junctions

So we're not fully appreciating, the three-dimensional structure, but the basic idea is that maybe the cell on the left, starts producing some molecules, especially some small molecules, that are able to go through these gap junctions

And when they're able to go through the gap junctions, maybe they latch on to some proteins in the second cell, that start maybe activating them in a certain way, or inhibit them in a certain way, or trigger some type of reaction

And so then you have a response in the second cell

Something happened in this first cell, to produce these molecules

Those molecules were able to get into the second cell, and trigger a response

And as I mentioned, if these are animal cells, we would call these gaps, we'd call them gap junctions

So that right over there, that is a gap junction

And if we're talking about plant cells, we can have very similar things happening, but we wouldn't call them gap junctions

These would be gaps, not even tunnels through the membrane, it would also be through the cell walls

And we'd talk about these more, in The Structure of Cell videos

You could imagine maybe some cells, that are floating around in the blood stream

Maybe this is one cell over here, maybe this is another cell over here

Transcripts

- [Voiceover] What I wanna do in this video

is give ourselves a quick overview of the different ways

that cells can communicate with each other.

And maybe the most basic one,

is just through direct contact

and this can happen several different ways.

One way could be,

you just have neighboring cells

so this is one cell right over here,

and this is the neighboring cell right over here.

And they actually might have gaps in their membranes.

If these are plant cells

we would call these gaps, gap junctions.

I just drew two of them and this is obviously

just a two-dimensional slice.

So we're not fully appreciating

the three-dimensional structure,

but the basic idea is that maybe the cell on the left

starts producing some molecules,

especially some small molecules

that are able to go through these gap junctions.

And when they're able to go through the gap junctions,

maybe they latch on to some proteins in the second cell

that start maybe activating them in a certain way,

or inhibit them in a certain way,

or trigger some type of reaction.

And so then you have a response in the second cell.

So this would be a form of communication.

Something happened in this first cell

to produce these molecules.

Those molecules were able to get into the second cell,

and trigger a response.

And as I mentioned, if these are animal cells,

we would call these gaps,

we'd call them gap junctions.

So that right over there,

that is a gap junction.

And we covered this in other videos.

And if we're talking about plant cells

we can have very similar things happening,

but we wouldn't call them gap junctions.

These would be gaps,

not even tunnels through the membrane,

it would also be through the cell walls.

If we were talking about plants,

they would be plasmodesmata.

And we'd talk about these more

in The Structure of Cell videos.

But there is other ways that you could communicate

via direct contact.

You could imagine maybe some cells

that are floating around in the blood stream.

Maybe this is one cell over here,

maybe this is another cell over here.

And they have complementary surface proteins.

Surface proteins that are able to bind to each other.

So maybe this one has a surface protein

that looks like this.

I'm obviously exaggerating its shape,

the protein wouldn't look exactly like

this inverted triangle.

But this one has a surface protein like this,

and I'm also exaggerating it's size relative to a cell,

just so we can appreciate

how they could maybe lock together.

So this one has a surface protein like that.

And when they bind to each other

it might change the proteins in some way,

and then trigger a reaction in each of these cells.

That the communication then continues.

If this protein changes a little bit,

it might activate something.

It might activate the release of some molecules,

it might activate some other proteins,

it might catalyze some type of reaction.

We've seen this in multiple other videos,

all sorts of crazy biological reactions

can happen inside of cells.

But it might illicit a,

it could illicit a response.

And actually it could even illicit a response in both cells,

some type of response.

They know that they are latched-on to someone else.

Now direct contact you could imagine,

is not the only way that you could have cell-cell signaling.

You could actually have cells start to signal

over a little bit of a distance,

by releasing molecules into the extracellular space

and eventually even into the blood stream.

So, for example,

let me draw a cell right over here,

and maybe it's able to produce some molecules.

And these molecules either,

they might be lipid soluble and maybe make their way

through the cellular membrane on their own.

Or, maybe they are packed in nice vesicles

that allow them to traverse the membrane.

So when you get actually,

so the membrane of the vesicle

merges with the membrane of the cell.

And then it allows

these things to get out.

And so you could imagine,

if another cell has the right receptors for these,

that would signal some type of a response

or it will form some form of communication.

So let's say that I have,

actually let me draw a couple of cells.

So let's say I have this cell over here,

and then I have this cell over here.

And let's say that this cell has the right receptor,

and this cell doesn't.

It could have other receptors,

maybe it has receptors like that

but it's not the right receptor.

And so these molecules that were released by this first cell

could bind not on this character,

not on this surface protein,

but it could bind on this character.

So it could bind on this character

and when it does so,

this protein that's on the cellular membrane,

it might change its shape,

it might do all sorts of things.

But that signal can be then taken somehow,

it can continue on into the cell and once again,

you might illicit some type of response.

And we'll go into more detail in future videos

on exactly how that happens,

or what these responses actually might be.

Now, if this is over a short distance,

if this is a short distance,

short distance,

we would call this paracrine.

This would be part of the paracrine system,

or we would call this paracrine communication.

Let me write that down,

paracrine system,

or paracrine communication,

or paracrine signaling,

and we would call these paracrine factors.

But if it was happening over long distances,

say maybe these molecules

they enter into the blood stream,

so they make their way into the blood stream

right over here.

So let me depict somehow that this is the blood stream.

So this is the blood stream,

and they're able to go through the blood stream

over longer distances to other molecules.

So maybe this one has the right receptors

for those molecules.

Then we'd call this the endocrine system,

or this is endocrine signaling.

So long distances,

we would call this the endocrine system,

or endocrine signaling.

And we're talking about the endocrine system

and endocrine signaling,

these molecules which could just be,

there could be all sorts of different types of molecules.

They could be steroids,

they could be proteins of some kind.

In this case, we would call them hormones.

And you've probably heard the word before

and we will do a whole series of videos on hormones.

But these molecules actually could even affect

the cell that produced them.

For example, the cell that produced it

might have the right receptor.

And so, if it's able to signal,

if it's able to trigger a reaction in itself,

so if these things are able to trigger a reaction in itself,

we would call that an autocrine process.

It is acting on itself.

And just so you're familiar with some of the terminology,

these proteins on the surface,

and this would be the case especially if you have

non-lipid soluble types of signaling factors,

or molecules right over here.

These proteins, actually even if they're on the surface

or even if they're within the cell,

we would call them receptors.

So that right over there,

that is a receptor.

And the molecules themselves,

these things that bind on to the receptor,

we call them the ligand.

In general, it's the general term for something

that binds on to a receptor.

And so at that point where you bind on to a receptor,

whether you're talking about the paracrine process

or endocrine,

actually endo, I left a C out here,

endocrine signaling,

this process where it latches on,

we would call that a signal perception.

And then when this protein somehow changes its shape,

or starts catalyzing a reaction,

or inhibiting a reaction,

we would call this the signal transduction.

It's bringing the signal into the cell.

And then you have,

you have your actual cellular response.

So hopefully you appreciate that

as just a bit of an overview

of how cells can signal with each other.

And in future videos we'll go into a little bit more detail.

Especially the endocrine system,

and our understanding of hormones.